When I was at the age when my friends were having babies, I enjoyed the imagination and creativity of my friends, turned parents. When visiting a good friend who had a toddler, my first surprise was the banana she gave her boy. Seconds later I was wondering what happened to the banana. I really was concerned and tried to discover if he had dropped it or possibly was choking on it. She hadn't missed a beat. Yes, he ate it, at a rate I still haven't fully decided was for real.
Another friend was showing off her firstborn daughter, and her ability to smear and eat equal amountsof a PB&J sandwich. She handed her daughter a fine wet cloth and we continued visiting. A few minutes later she exchanged the cloth and I realized that by handling the wet cloth, she was cleaning up impossibly small hands and her untouchable face. The baby was unaware that she was cleaning up, it was just what babies do.
For reasons I will never understand, when my little sister had a full snot locker before the concept of "blowing" her nose had been learned, my father had the unenviable job of clearing out her tiny nose with a bulb syringe. My mother couldn't stand the thought of doing it herself, and for a baby who saw me as her personal enemy, I was her second choice of nasal torturer. My father and I used to do it together, in part because it relieved mom of the duty and I was strong enough to hold her down.
He had coached me on sucking snot with a minimum of pain. I always squeezed the bulb well before popping the plastic tube of the device into a nostril, releasing the bulb just when the nostril was about to seal against the tapered tip, while simultaneously withdrawing the entire bulb syringe. Two goals of using the viscosity of the mucus to remove everything in one slick move just fast enough not to tug at the eardrums. I was amazed she submitted to my torture, Daddy had her absolute trust but I had to be called on the rare occasion to do it and she accepted this. One time I was holding her after a difficult cleaning, tears and bawling from the unpleasant experience, she thanked me. Wow!
She could be a serious handful when we had to get her primed to the idea of what we were going to do. Somehow she figured out how obeying "now hold still" was to her advantage but the struggle getting there would be a problem, especially when she couldn't associate breathing better with the torture.
The alternative that I can suggest is a personal steamer. One Christmas I got my mother a Sunbeam Facial Sauna. It's still available as I bought it some 52 years ago from Sunbeam and other manufacturers, not surprisingly at Walgreens. I'm not sure if this is better than a sinus rinse but I am guessing that he will find it soothing. I've seen TV ads for a personal steamer and it has the advantage of fitting sort of like a pediatric nebulizer "mask". Today I priced a personal medical steamer at a whopping $150 from Target, it's not cheap. I love the fact that the facial sauna warms the sinuses, outside and in, the entire face outline rests on a gasket. He might find some custom aroma therapy. Something to encourage smell, and inhaling through the nose, like vanilla and then something to encourage mucus production like camphor. I'm not an aroma therapy enthusiast or expert but I have worked with many methods of cleaning the nasal passages and I have used everything from mentholated petroleum jelly to my own concoction of an antibiotic rinse. CF almost always impacts the nasal passages because of the hyper-viscous mucus and its function of being a microbe trap. Avoiding sinus reconstruction surgery in future years may be impossible, but sinus cleaning is extremely important. Steam and stimulating mucus clearing is in my top 4 or 5 long term CF regiments. Done daily it reduces ENT infections as well as lung and stomach bugs.
Steam is going to be a great help, not as thorough as a sinus rinse but something he is probably will like. Even my friend with 2 autistic boys were users of the facial sauna.
LL
P.S. I'm happy to talk via PM, anytime.